Time Warner, History Channel, Military Channel, Google the subject and see what is out there.
I don't know where to buy them, but when I'm lookinh for historical footage of that nature I go to the Internet Archive.
Thousands of movies and such. I'm sure at least part of what you're looking for can be found there.
Other people asked questions on similar topics, check out the answers they received:
Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them